Do you make your own alloy? So you know there is no cadmium?
A stupid question: Why are you using green gold for a part of a piece that you want to be yellow…? Can’t you use green gold for the green part and yellow gold for the yellow part? I know it would be easier if the whole piece is one alloy, but when you want colors other than yellow, your best bet is a lower karat gold (for a deeper non-yellow color), while higher karat golds are of course better for yellow…
Yup. . .I make it myself 
The reason I use it though is because it is optimal for the 18k granulation I do. If I recall correctly, the extra silver gives a broader temperature range between the solidus and liquidus points making it easier to “fuse” (not actually fusing since I use curpric carbonate, but it’s pretty darn close in terms of behavior under the torch, tolerance required for joints, etc. so it’s just easier to use the term).
Good Day Erich,
As said in one of the replies, Sulfuric acid ( have always used lab grade)
heated , on the heater plate in a beaker and then the piece dipped in by
slinging it on a copper wire, gives very good rich yellow. (have also tried
it on 18 K white and the result was bright rich yellow.
Plating (flash) does not give you consistent results, but this does one
word of caution please do it in a very well ventilated room,as the emerging
fumes are nasty.please do take lot of caution.
Regards,
Khushroo H.Kotwal
Here is Rhonda Coryell’s formula for 22kt
granulation:
For granulation, the following formula is preferred:
Pure Copper 0.5 dwt ( Fig. 1)
Fine Silver 1.5 dwt ( Fig. 2)
24kt Gold 22 dwt (Fig. 3)
The quantity of 22kt produced is 24 dtw total weight.
From Harold O’Connor, who does a lot of gold granulation, for 18kt. granulation:
75% fine gold, .019% fine silver, .06 copper.
When sterling silver is heated and turns black, it is sulfide forming. It is not oxidation.
Heating metal and throwing it in sparex is not a good idea, quenching in water and then putting it in sparex will accomplish the same thing.
Precisely what I’ve been saying/realizing. . . . when it comes to silver, it isn’t oxide that’s forming, it’s sulfides. The catch here is that those aren’t really forming either (unless you introduce sulfur). Technically, there’s going to be trace amounts floating around, but not enough to matter. This is further evidenced by the fact that Sparex (sodium bisulfate) won’t attack sulfides. The fact that you can heat a piece of sterling or 18k to near black, throw it in a pickle of Sparex and have it come out clean is proof that there aren’t any sulfides forming. What all this means is that about 99% of any dark residue formed during soldering jewelry alloys are brought about by base-metal oxides, not silver oxides and/or sulfides. . . if I’ve understood everything correctly so far that is. Which also means that using standard gilding techniques on green gold won’t really have the effect I want since the silver won’t oxidize meaningfullyto be removed by a pickle or form sulfides that could be removed with thiourea based cleaners. So far, its looking more and more like I’m going to have to get some nitric acid or perhaps ferric nitrate.
Sounds like O’Connor uses the same recipe as me (I’m assuming the decimal places just got accidentally moved since it otherwise wouldn’t add up to 100%).
One more attempt with my initial solution, but this time I’m going to heat the hell out of it (or into it as the case may be). . .
Thanks for the additional info! I’ll let everyone know what I find out in case someone else eventually goes down this road covered in brambles, thorns, and the occasional exposed root to trip over.
Erich
Success!! I managed to get the original recipe to work, but I had to get it not just warm, but hot, hot, hot. . .just under a boil. Funny thing is that I’m not entirely certain of what it is doing. On the one hand, it is supposed to be depletion gilding the surface by removing the silver (for the most part). If that was the case, I would’ve expected the surface to end up somewhat frosted, but it isn’t. The polish is still there, but the green is gone.
A few notes, this was done in a pyrex container and the only other metal introduced was a wire of the same 18K green gold alloy to suspend the piece with. So I know nothing was contaminated and I don’t think anything is being plated (ala copper plating after iron has been dropped in the pickle), but I do find it strange that the finish is being preserved even though I’m getting rid of the greener tones.
Well, either way, I’m happy to have figured it out and learned a fair amount along the way. Thanks everyone for the help! As always, it’s much appreciated!
Erich
Thanks Khushroo. I appreciate the idea.
Tom Arnold, I believe mercury/gold amalgam was used to gild objects, not to depletion gild.
What is Mercury Gilding/Silvering?
Mercury is a metal that is liquid at room temperature. When combined with gold or silver, it becomes viscous, its consistency becoming similar to that of butter. Mercury gilding is the process in which mercury is mixed with gold to make an amalgam that is applied to the surface of an object. (Mercury silvering uses the same process, but the mercury is mixed with silver.) When the object is then heated in an oven or over a fire, the mercury evaporates and leaves behind a thin coating of gold or silver. The evaporation process results in bubble-shaped cavities forming within the coating, requiring a final burnishing step to make it smooth.
Richard Hart
That’s correct. You can see an example of it in this video. It starts at the 5:50 mark
Oh Geez! Well now. That’s a pretty humbling video.
Now I’m ready to burn all of my tools and chop my hands off at the wrist:-)
Jo Haemer
No kidding. . . . I think I could watch that video series all day long.